The present invention relates in general to an assembly for adhesive attachment to the skin or mucosa of a host. More particularly, the present invention relates to transdermal patches and wound dressings, and to methods for their manufacture. Still more particularly, the present invention relates to improvements in the manufacture of adhesive patches.
The use of various systems for adhesive attachment to the skin or mucosa of a patient or host has become increasingly significant. These assemblies can be in the form of wound dressings for direct adhesive application to the skin, without any active agent therein, or transdermal patches for the transdermal delivery of various active agent or drug systems in connection with such attachment. In connection with the general means for preparing such assemblies, there has been an increase in the need to facilitate the handling of adhesive containing assemblies or patches, and for then maintaining them as separable units. In connection with transdermal patch systems, there have been problems engendered by the use of various drugs in which the drug is employed in admixture with an adhesive-based system for application to the skin, or with a non-adhesive-based system with an outer drug permeable adhesive layer.
Simple monolithic transdermal systems incorporate their active agents, i.e., drugs, directly into a single pressure-sensitive adhesive layer. These systems have the advantage of being thin, elegant, and relatively easy to manufacture, but must compromise between optimizing the adhesive matrix for drug delivery versus its ability to adhere to the skin. In addition, these systems still present challenges in connection with their large volume handling and manufacture.
The known “double-disk” transdermal patch uses a larger auxiliary patch over a smaller active agent delivery patch to improve or ensure adhesion to the skin. The adhesive matrixes of the inner and outer patches can be independently optimized for active agent delivery and adhesion, respectively. When the inner and outer patches are laminated together to form the completed system, their adhesive matrixes come into direct contact and begin to equilibrate. As the systems equilibrate, time-dependent changes occur such as the loss of active agents from the inner patch and the simultaneous accumulation of active agents in the outer patch. This phenomena can alter the performance of the transdermal patch if any of the components in the inner patch, especially those that are needed to achieve or sustain active agent delivery, have appreciable affinity for the outer patch adhesive matrix. Moreover, this effect will become more profound with time until equilibrium is achieved.
One solution in preventing the equilibrium of the two adhesive matrixes is to maintain their physical separation, and not to allow the adhesives to come into direct contact with each other during storage. Following application to the skin, these adhesive matrixes will be in direct contact, but the equilibrium process, typically two-three years, is slow compared to the transdermal delivery process, generally less than or equal to seven days. However, in the double-disk transdermal patch, the circumferential edge of the inner patch containing the active agent is exposed to the overlying outer patch and its adhesive matrix. This structure of the double-disk transdermal patch allows for the circumferential migration of active agent from the inner patch into the adhesive matrix of the outer patch.
A solution to some of these problems is set forth in U.S. Patent Publication No. 2005/0037059, which is owned by the assignee of the present application. This application discloses the use of a physical barrier between the patches during storage so that the migration of active agents is inhibited between the inner and outer patches. In accordance with this disclosure, the inner and outer patches are adhered together in a manner creating an annular flap circumferentially about the outer portion of the inner patch and a disposable release liner is interposed between the annular flap and the adhesive material of the outer patch. The outer flap, which contains the active agent, is thus said to be isolated from the underlying portion of the outer portion by the release liner which is releasably attached to the adhesive on the outer patch. This product has proven to be quite successful, but a desire still exists for a more efficient product for completely segregating the annular flap containing the active agent from the underlying portion of the outer patch.